[Consistency in viabilities of mycobacteria detected by FDA/EB staining and colony forming units on the medium].

We have previously reported that the staining of mycobacteria with fluorescein diacetate (FDA) and ethidium bromide (EB) detects viable bacteria and distinguish them from heat-killed bacteria. Whether this method can be applied to clinical specimens has been an important question. In the present experiment, we treated mycobacteria with either UV-irradiation, 70% ethanol, 0.2% benzalconium chloride, 5% saponated cresol solution, or 5% phenol for 24 hours, and stained with FDA/EB to evaluate the effect of sterilization. We also stained samples of sputum from a tuberculosis patient with FDA/EB after treatment with 4% NaOH for 30 min. and neutralized with 1N H2SO4. All the samples were determined for the colony forming units on 1% Ogawa egg media. A good correlation was observed between the results of FDA/EB staining and colony formation. We believe that FDA/EB staining is useful method to detect viable mycobacteria in clinical samples.